In many types of diode-based solid-state memory, each memory element includes a p-n junction diode. A switching device (that includes, for example, a phase-change material) may be combined with the p-n junction diode to create a reversibly switching, re-programmable (i.e., rewritable or read-write) phase-change random-access memory (“PCRAM”) element. The switching device is typically formed in a recess adjacent to each p-n junction diode. In the prior art, the recess is formed using a subtractive process wherein at least one film layer is deposited, masked with a lithographic process, and partially removed with chemical etching. A conventional complementary metal-oxide-silicon (“CMOS”) based phase-change memory requires sixteen or more masks.
Other PCRAM processes may require even more photomask steps. Each photomask adds to the cost, complexity, time, and likelihood of failure of the overall device processing. A need exists, therefore, for a PCRAM processing method that uses fewer photomask steps and is thus cheaper, simpler, faster, and more robust than existing processes.